Cook bacon pieces in a large cast iron skillet. Drain the grease, leaving 2 – 4 tablespoons in the pan.
In the same pan, add the sliced onions. Toss to coat with bacon grease. Over medium-low heat, cook the onions until they are a deep brown color and caramelized, stirring frequently. This will take about 45 minutes to an hour. Don’t rush it! The longer they cook the more flavor it will add.
Add the brown sugar and balsamic vinegar to the pan. Don’t forget to scrape the bottom to get up all the good cooking bits. This adds flavor! lots of it!
Continue to stir until the liquid reduces by about half. This will take about 5 minutes.
Add salt and pepper to taste.
Spoon the delicious Bacon Onion Jam into a mason jar and let it chill in the fridge until you are ready to add it to your perfect burger.
Will keep for a week or two sealed in the fridge. (If it lasts that long!)